I'm a South African, living in SA, so I'd like to comment on some of the replies here.
Firstly, it wasn't a South African man. He was Mosambican. Like too many others in this country. It's horrific what happened, but to put some things into perspective in this wild country of ours. There's zenophobia going on BIG TIME. People stream into our country from their (even worse) Northern African countries. And take the jobs away from South Africans. The poor gets extremely upset about this. And the government does nothing to help them or prevent illegal immigrants. About a quater of Zimbabwe has spilled into South Africa with the decline of their own country just in the the past decade.
Secondly, this does NOT happen regularly. Though, we have MAJOR problems with police taking the law into their own hands. It's came to the point where I'm a little scared of the police. But the only other case I know of someone being dragged recently, was the dead body of a man, the dead body of a dog, and before that, a woman being run over by a taxi driver and dragged. He did it on purpose, and the case is still in court. She fortunately (mostly) healed, as well as one could heal from being rip to shreds.
Thirdly, this man most likely didn't "just" park at the wrong side of the road. Police struggle on a DAILY basis with taxi drivers doing JUST what they want to. They cause daily accidents in our country, and almost never abide by the rules. All that matter to them, is getting to as many passengers as possible, to meet their targets to give to the taxi bosses and take their own meagre pay home. Or the taxi boss takes his taxi away from him. So their driving is horrific and has led to way too many road deaths. Pressure are put on police to take care of the taxi problem, but obviously, this wasn't what was meant by that!
Fourthly. We DO have a working justice system. A pretty good and fair one! Unfortunately, it's been under severe pressure the past 20 years due to the ANC's maladministration and their meddling into the independance of the judicial system. They try to appoint "their" cadres whereever they can, which leads to major problems. But, somehow, we're still able to mostly have fair trials.
It's true though that witnesses WILL be bribed/intimidated/etc. and they will be scared to speak up. Very very alarming and sad.
I hope this incident does force the ANC government to really look at the decline of the police force and do something about it. Because if they don't, we're going the way of some of the other African countries and that saddens me so so much.